[T3] Engine Rattling.... Update...

[Bobsnotch at aol.com]

In a message dated 5/25/2012 6:17:35 P.M. Eastern Daylight Time,  
j_jonik at yahoo.com writes:

Re/  71 sqbk FI Std shift....with a seemingly worsening rattle in  engine 
area.

A  good diagnosis and explanation came in over the  phone from a mechanic 
who's worked on the old bombs for decades. He knew just  the sound I 
described...tinny, like a rattle-snake, when changing  gears  and at idle...not when 
driving steadily.

Yes...(as explained here not  too long ago) it's about too much play in the 
crank shaft, as seen by moving  the fan pulley in and out.   It's largely 
about old age of the  engine....as the bearing dowel holes in the case have 
gotten a bit elongated  and are not holding the bearings, and the crank, 
snugly any more.  How  four dowel holes can wear out is a mystery.
He figures the case is  shot.   But, to be picky, a few more questions...

* Exactly  what thin-sounding metal parts are rattling together?  
*  Any  chance it's not the case, but the bearing shells? Or do both dowel 
holes get  out-of-shape at once?
*  No leaks from oil seal...yet....but will that  be drastic (can't drive 
home) or gradual?
*  Engine does not have as  many miles on it as some others.  This one had 
only 60 thou, or less,  when I got it...and I may have put that much again 
on it  AFTER new  pistons and cylinders.  What is normal life span vis a vis 
mileage?   Or does this have anything to do with careless assembly ten years 
ago, or bad  driving practices?
*  Would it have helped if case nuts (top and  bottom, front and back) were 
checked and re-torqued (if needed) every so  often?  (Don't know yet if 
they aren't as tight as should  be.)

I have a spare engine in '73 parts car.  I  haven't checked its crankshaft 
play yet.  Fingers crossed.  Didn't  rattle when I parked it ten years ago.



Yes, it's possible that the engine has too much end play. But the only way  
to know how much is too much is to pull the engine. Otherwise you're just  
guessing. Where you'll get sound from would be the throw out bearing, and 
the  small cooling fan rubbing on the fan housing.It's also possible that the 
dowel  pins are rocking in their bores, as the crank moves forward and  
backward with the end play, as you accelerate, and decelerate. That might  also 
be the times you're hearing the rattle. I don't know. I haven't heard  it.
 
No the bearing shells are the bearings, and are located in the case by the  
dowel pins. The 2 case halfs compress into place to hold the bearing shells 
in  place.
 
If it's not leaking oil, I'd have to guess that end play isn't that large,  
or the seal is really doing a nice job of sealing, as they'll get a slight 
leak  as the seal wears a spot in the seal (from sliding back and forth 
across  it).
 
If you're figuring that you have approximately 120K miles on it, then it  
might be getting close to a rebuild. As Keith will point out, the heads 
should  be rebuilt every 60K or so. And if you're doing that, then the rest of 
the  engine should be torn down, inspected, and possibly rebuilt.
How many miles you'll get out of it, in it's current condition are unknown. 
 It could quit tomorrow, or next year. I've had a rod bearing seize on a 
fairly  new engine before (less than 500 miles after being rebuilt), and I've 
had a  valve head come off (twice) that destroyed 1 cam, and the other broke 
the  case.Both of those engines had at least 60K on them.
If you know what the rattle really is, then you might just want to drive it 
 until it quits.But the key is finding out what the real issue is.That 
might  require taking the engine out though.
 
Torqueing the top and bottom case half nuts and bolts wouldn't have helped  
a bit.
 
If you're really worried, I'd dig that spare engine out, and possibly go  
thru it, so that it's ready to go into the car when you're ready (before the  
existing one quits).
 
Have you checked all of the engine tin to make sure it's not cracked and  
rattling. Or that the exhaust shielding isn't rattling. I'm only asking, 
because  these are the first places I'd look, with the generator bearing being 
after it  (if I still had a rattle).
 
Bob 65 Notch  S with sunroof and IRS (Krusty)
64 T-34 Ghia  (Wolfie)
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